1. Field of the Invention
This invention relates generally to a fenestration unit which does not include an insulated glass unit (IGU). More specifically, the glass panes are placed directly into the sash without first being permanently and structurally fastened to each other by a spacer. This invention also includes a method for manufacturing a fenestration unit without the utilization of an IGU.
2. Description of the Prior Art
Early fenestration units, including windows and doors, only had a single pane of glass. Typically, the glass would be placed in the sash and then a glazing material would be applied to hold the glass into the sash. However, in more recent times, two or more panes of glass have been utilized in windows for better insulating value. A gap between any two glass panes creates further insulation. The prior art teaches the use of a separate spacer between the two glass panes to structurally support the two panes of glass and also to create such a gap. This combination of two panes of glass with a structural spacer between them resulted in an insulated glass unit which was a separate subassembly from the sash or frame. It did not use any features of the sash or frame to achieve its structural strength, thermal properties or in maintaining the sealed space between the two glass panes.
FIG. 1 illustrates a typical IGU 10 of the prior art. A first glass pane 11 is sealed to one end of spacer 12 with a sealant 14, and a second glass pane 16 is sealed to the other end of spacer 12 with sealant 14. The spacer 12 can be of many different shapes and materials but is often made of aluminum as shown in FIG. 1. It should be noted that the prior art spacers can be hollow and filled with a desiccant. The combination of two or more glass panes separated by a spacer is manufactured as a unit (IGU 10) and then later placed into the sash of the fenestration unit.
FIG. 2 illustrates the IGU 10 after it has been placed in the sash 17 of a fenestration unit.
The prior art fenestration units have a number of problems. Manufacturing involves two operations in which the first operation is manufacturing the IGU and the second operation is placing the IGU in the sash. This dual operation process incorporates significant cost into the fenestration unit. Additionally, this dual operation process typically involves shipping glass from the glass factory to the window manufacturer in the form of an IGU. Such a dual operation process creates a greater potential for glass breakage and the IGU's take up more shipping space than the transport of individual glass panes. Additionally, despite efforts to minimize thermal conductivity through the spacer 12, there continues to be significant heat loss through the spacer 12. There is significant heat loss because the spacer must be thick enough to structurally separate the two panes of glass and a thick spacer conducts more heat than a thin spacer.